Mattermost Team ID Change Bypass in Playbooks

Executive Summary

This vulnerability affects Mattermost versions 11.5.x up to 11.5.1 and 10.11.x up to 10.11.13. It occurs because the software fails to verify whether the {{team_id}} field is being changed when updating playbooks. As a result, users who have only the Manage Playbook Configurations permission can change a playbook's associated team. This bypasses the intended restriction on managing members via the PUT API.

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Impact Analysis

The impact of this vulnerability is that users with limited permissions (specifically, only Manage Playbook Configurations) can change the team associated with a playbook. This allows them to bypass restrictions that normally prevent them from managing members of that team, potentially leading to unauthorized changes in team configurations or access.

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Mitigation Strategies

To mitigate this vulnerability, you should update Mattermost to a version later than 11.5.1 for the 11.5.x branch or later than 10.11.13 for the 10.11.x branch, where the issue has been fixed.

Additionally, review and restrict permissions related to managing playbook configurations to trusted users only, as the vulnerability allows users with Manage Playbook Configurations permission to bypass manage members restrictions.

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